U.S. patent application number 10/849775 was filed with the patent office on 2004-12-02 for card device with a sweep-type fingerprint sensor.
Invention is credited to Chou, Bruce C. S., Tsou, Chingfu.
Application Number | 20040238647 10/849775 |
Document ID | / |
Family ID | 33448939 |
Filed Date | 2004-12-02 |
United States Patent
Application |
20040238647 |
Kind Code |
A1 |
Tsou, Chingfu ; et
al. |
December 2, 2004 |
Card device with a sweep-type fingerprint sensor
Abstract
A card device includes a substrate having two long sides and two
short sides, and a sweep-type fingerprint sensor embedded into the
substrate. The sweep-type fingerprint sensor has an exposed
fingerprint sensing surface, and is disposed in a rectangular
low-stress region. The rectangular low-stress region has a
dimension substantially smaller than or equal to 30 mm*22 mm. The
shortest distance from the low-stress region to each long side is
substantially equal to 2 mm, and the shortest distance from the
low-stress region to each short side is substantially equal to 2
mm.
Inventors: |
Tsou, Chingfu; (Hou Li
Hsiang, TW) ; Chou, Bruce C. S.; (Hsin Chu,
TW) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
33448939 |
Appl. No.: |
10/849775 |
Filed: |
May 21, 2004 |
Current U.S.
Class: |
235/492 |
Current CPC
Class: |
G06K 19/077 20130101;
G06K 19/0718 20130101 |
Class at
Publication: |
235/492 |
International
Class: |
G06K 019/06 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2003 |
TW |
092114621 |
Claims
What is claimed is:
1. A card device, comprising: a substrate having two long sides and
two short sides; and a sweep-type fingerprint sensor, which is
embedded into the substrate and has an exposed fingerprint sensing
surface, wherein the sweep-type fingerprint sensor is disposed in a
rectangular low-stress region having a dimension substantially
smaller than or equal to 30 mm*22 mm, the shortest distance from
the low-stress region to each of the long sides is substantially
equal to 2 mm, and the shortest distance from the low-stress region
to each of the short sides is substantially equal to 2 mm.
2. The card device according to claim 1, wherein the rectangular
low-stress region has the dimension substantially smaller than or
equal to 22 mm*22 mm.
3. The card device according to claim 1, wherein the rectangular
low-stress region has the dimension substantially smaller than or
equal to 22 mm*14 mm.
4. The card device according to claim 1, wherein each of the short
sides has a length substantially equal to 56 mm.
5. The card device according to claim 4, wherein each of the long
sides has a length substantially equal to 86 mm.
6. The card device according to claim 1, wherein the fingerprint
sensing surface is configured such that a finger sweeps across it
in a direction, which defines an angle with each of the long
sides.
7. The card device according to claim 6, wherein the angle is
substantially equal to 90 degrees.
8. The card device according to claim 6, wherein the angle is
substantially equal to 0 degrees.
9. The card device according to claim 6, wherein the angle is
substantially equal to 45 degrees.
10. The card device according to claim 6, wherein the angle is
substantially equal to that defined by a diagonal of the substrate
and each of the long sides.
11. The card device according to claim 1, wherein: a groove is
formed on the substrate; the sweep-type fingerprint sensor is
located in the groove; the groove is for guiding a finger to put
therein and guiding the finger to sweep across the sweep-type
fingerprint sensor.
12. The card device according to claim 11, wherein the fingerprint
sensing surface is configured such that the finger sweeps across it
in a direction, which defines an angle with each of the long
sides.
13. The card device according to claim 12, wherein the angle is
substantially equal to 90 degrees.
14. The card device according to claim 12, wherein the angle is
substantially equal to 0 degrees.
15. The card device according to claim 12, wherein the angle is
substantially equal to 45 degrees.
16. The card device according to claim 12, wherein the angle is
substantially equal to that defined by a diagonal of the substrate
and each of the long sides.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a card device with a fingerprint
sensor, and more particularly to a card device with a sweep-type
fingerprint sensor.
[0003] 2. Description of the Related Art
[0004] In order to prevent the syndicate from counterfeiting the
smart cards such as credit cards, personal identification cards,
driver's licenses, passports, social welfare cards and health
insurance cards, every card issuer has to spend a lot of resource
to protect the smart cards with strict security designs. Because
the fingerprint is the personal biometric data and cannot be easily
counterfeited, the smart card embedded with the fingerprint sensor
becomes one of the mainstream development in the future.
[0005] All the fingerprint sensors embedded in the conventional
card devices belong to the two-dimensional (2D) sensor. That is,
the fingerprint sensor can acquire the finger's fingerprint image
as long as the finger statically contacts the fingerprint sensor.
For instance, the card devices disclosed in U.S. Pat. Nos.
4,582,985 and 6,494,380 utilize the 2D fingerprint sensors. Owing
to the dimensional limitation of the finger, the sensing area of
the conventional 2D fingerprint sensor is at least greater than 9
mm*9 mm. Furthermore, owing to the limitation in the dimension of
silicon wafer, only 50 to 70 effective chips may be produced in a
6" wafer. The selling price of the single fingerprint sensor is at
least greater than 10 U.S.D. with the packaging and testing costs
included therein, which will limit the usage of the card device
embedded with the fingerprint sensor.
[0006] Because the smart card is a portable device, the user may
unintentionally apply external forces to the smart card to make it
bent or twisted. In this condition, the fingerprint sensor embedded
in the smart card may be caused an extreme stress and thus damaged
or even fractured. In order to solve the above-mentioned problem,
U.S. Pat. No. 6,494,380 discloses a 2D fingerprint sensor that is
also composed of a plurality of sensing blocks. Although the
problem of the sensor damage in the twisted or curved card device
such as the smart card may be solved, the fingerprint image
distortion will be caused owing to the spacing between two adjacent
sensing blocks. When the most important minutia pattern of the
fingerprint is located in the spacing, the fingerprint identifying
operation cannot be really completed.
[0007] Thus, it is an important subject to provide a low-cost card
device (e.g., a smart card) embedded with a fingerprint sensor that
cannot be easily damaged.
SUMMARY OF THE INVENTION
[0008] It is therefore an object of the invention to provide a
low-cost card device having a sweep-type fingerprint sensor that
cannot be easily damaged.
[0009] The invention achieves the above-mentioned object by
providing a card device including a substrate having two long sides
and two short sides, and a sweep-type fingerprint sensor embedded
into the substrate. The sweep-type fingerprint sensor has an
exposed fingerprint sensing surface, and is disposed in a
rectangular low-stress region. The rectangular low-stress region
has a dimension substantially smaller than or equal to 30 mm*22 mm.
The shortest distance from the low-stress region to each long side
is substantially equal to 2 mm, and the shortest distance from the
low-stress region to the short side is substantially equal to 2
mm.
[0010] The substrate is preferably formed with a groove, in which
the sweep-type fingerprint sensor is positioned, wherein the groove
is for guiding the user to put his/her finger therein, and guiding
the finger to sweep across the sweep-type fingerprint sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows the stress-strain relation of a silicon
substrate of a sweep-type fingerprint sensor of the invention.
[0012] FIG. 2 is a top view showing a card device with a sweep-type
fingerprint sensor of the invention.
[0013] FIG. 3 is a front view showing the card device with the
sweep-type fingerprint sensor of the invention.
[0014] FIG. 4 is a side view showing the card device with the
sweep-type fingerprint sensor of the invention.
[0015] FIG. 5 is a pictorial view showing the card device with the
sweep-type fingerprint sensor of the invention.
[0016] FIG. 6 shows the stress distribution result of a curved
state of FIG. 3.
[0017] FIG. 7 shows the stress distribution result of a curved
state of FIG. 4.
[0018] FIG. 8 shows the stress distribution result of a curved
state of FIG. 5.
[0019] FIG. 9 is a top view showing a card device according to a
first embodiment of the invention.
[0020] FIG. 10 is a top view showing a card device according to a
second embodiment of the invention.
[0021] FIG. 11 is a top view showing a card device according to a
third embodiment of the invention.
[0022] FIG. 12 is a top view showing a card device according to a
fourth embodiment of the invention.
[0023] FIG. 13 is a partially cross-sectional view showing a card
device according to a fifth embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] A card device having a sweep-type fingerprint sensor has
been disclosed in the commonly-assigned U.S. patent application
Ser. No. 10/793,929, filed on Mar. 8, 2004, and entitled "CARD-TYPE
BIOMETRIC IDENTIFICATION DEVICE AND METHOD THEREFOR." A sweep-type
fingerprint sensor adapted to a card device has been disclosed also
in the commonly-assigned U.S. patent application Ser. No.
10/441,022, filed on May 20, 2003, and entitled "SWEEP-TYPE
FINGERPRINT SENSOR MODULE AND A SENSING METHOD THEREFOR."
[0025] FIG. 1 shows the stress-strain relation of a silicon
substrate of a sweep-type fingerprint sensor of the invention,
which are tested by way of three-point bending. The invention takes
7 silicon substrate specimens for test with the testing condition
of pressing down the middle point of the silicon substrate at the
speed of 0.001 mm/sec, and the test results are shown in FIG. 1. It
can be understood from FIG. 1 that the fracture strength of the
silicon substrate is about 350 MPa.
[0026] In order to realize the stress of the sweep-type fingerprint
sensor caused when the card device is bent or twisted, the
invention adopts the finite element method for analysis and
simulation. The simulated card device has the dimension of about
86*56*0.78 mm, which is the general card dimension all over the
world, and the fingerprint sensor is a 2D fingerprint sensor having
the dimension of 12*12*0.53 mm. The derived maximum stress cannot
exceed the allowable fracture strength of the fingerprint sensor.
It is to be noted that because the derived stress in the simulation
process is the maximum stress, the low-stress region suitable for
the 2D fingerprint sensor also may be regarded as being suitable
for the sweep-type fingerprint sensor.
[0027] FIGS. 2 to 5 are respectively top, front, side and pictorial
views showing a card device with a sweep-type fingerprint sensor of
the invention. Referring to FIGS. 2 to 5, the card device 1 of the
invention includes a substrate 2, which has two long sides 4 and
two short sides 5, and a sweep-type fingerprint sensor 3, which is
embedded into the substrate 2 and has an exposed fingerprint
sensing surface 6. In terms of the general standard specification
of the current card device 1, the length LX of the long side 4 is
86 mm and the length LY of the short side 5 is 56 mm.
[0028] In order to prevent the sweep-type fingerprint sensor 3,
which is embedded into the substrate 2, from being damaged when the
card device 1 is bent or twisted, the invention calculates the
maximum stress according to the physical properties of the
substrate 2 and the sweep-type fingerprint sensor 3, wherein the
calculated maximum stress cannot exceed the fracture strength of
the sweep-type fingerprint sensor 3. The sweep-type fingerprint
sensor 3 of the invention is usually made of silicon. The fracture
strength of the sweep-type fingerprint sensor 3 of the invention is
about 350 MPa according to the experimental test result. Thus, the
configurations are suitable for the invention as long as the
corresponding maximum stresses applied to the sweep-type
fingerprint sensor 3 are smaller than 350 MPa after the card device
1 is bent or twisted. For the sake of stress concentration effect
consideration, the stress safety factor is chosen to be 1.15. Thus,
the maximum stress of the disposed sensor cannot exceed 304
MPa.
[0029] Theoretically, when the card device 1 is bent or twisted,
the exerted stresses are the minimum at its four corners. So, the
card device 1 should be close to one of the corners as possible as
it can. The invention disposes a 2D fingerprint sensor with the
dimension of 12*12*0.53 mm on the card device 1, and makes the
analysis according to various disposing positions so as to derive
the maximum stress exerted on the 2D fingerprint sensor. The
above-mentioned maximum stress may correspond to the maximum stress
exerted on the sweep-type fingerprint sensor 3 of the invention
under the same condition. Herein, nine disposing positions are
proposed, as shown in the corner points of the positions P1 to P9
of the 2D fingerprint sensor. If the coordinate of the original O
is (0,0), the coordinates of the corner points of the positions P1
to P9 are respectively P1=(4,4), P2=(4,12), P3=(4,20), P4=(12,4),
P5=(12,12), P6=(12,20), P7=(20,4), P8=(20,12), and P9=(20,20).
[0030] The force-exerting simulation condition for the card device
1 is made according to the bending and twisting standard testing
specification of "ISO 7816 Standards for Cards," wherein the
associated analysis processes are described in the following. In
FIG. 3, two sides of the card device 1 are simply supported and a
downward force 2F1 is applied to the middle of the card device 1
such that the maximum deformation in the middle of the card device
1 is 2 cm downward. In FIG. 4, the two sides of the card device 1
are simply supported and a rightward force 2F2 is applied to the
middle of the card device 1 such that the maximum deformation in
the middle of the card device 1 is 1 cm rightward. In FIG. 5,
forces F3 are respectively applied to the four corner points of the
card device 1 such that the card device 1 is twisted .+-.15
degrees.
[0031] FIG. 6 shows the stress distribution result of a curved
state of FIG. 3. As shown in FIG. 6, the maximum stresses exerted
on the sweep-type fingerprint sensor 3 at positions P1 to P9 are
respectively 108, 114, 113, 167, 181, 180, 238, 259 and 258 MPa.
Thus, as the position of the sweep-type fingerprint sensor 3 is
closer to the perpendicular bisector of the long side 4, the
exerted stress is larger.
[0032] FIG. 7 shows the stress distribution result of a curved
state of FIG. 4. As shown in FIG. 7, the maximum stresses exerted
on the sweep-type fingerprint sensor 3 at positions P1 to P9 are
respectively 163, 263, 330, 170, 270, 314, 183, 295 and 330 MPa.
So, as the position of the sweep-type fingerprint sensor 3 is
closer to the perpendicular bisector of the short side 5, the
exerted stress is larger.
[0033] FIG. 8 shows the stress distribution result of a curved
state of FIG. 5. As shown in FIG. 8, the maximum stresses exerted
on the sweep-type fingerprint sensor 3 at positions P1 to P9 are
respectively 135, 148, 152, 148, 163, 169, 160, 176 and 182 MPa.
So, as the position of the sweep-type fingerprint sensor 3 is
closer to the center of the card device 1, the exerted stress is
larger.
[0034] It can be understood, from the above-mentioned results, that
the maximum stresses exerted on the sweep-type fingerprint sensor 3
at positions P3, P6 and P9 exceed 304 MPa. So, the sweep-type
fingerprint sensor 3 only can be located at the position of P1, P2,
P4, P5, P7 or P8, or any position among P1, P2, P4, P5, P7 and P8.
It also can be understood from the result that as the sweep-type
fingerprint sensor 3 is closer to the long side 4 or short side 5,
the exerted maximum stress is smaller. Therefore, the sweep-type
fingerprint sensor 3 may be theoretical located within the range
from the coordinates (0, 0) to (32, 24). However, owing to the
limitations of the manufacturing, packaging, testing and using of
the card device 1, the ranges that are too close to the long side
or short side are not suitable for the arrangement of the
sweep-type fingerprint sensor 3. According to this rule, the
portions within about 2 mm from the long side and short side are
not suitable for the arrangement of the sweep-type fingerprint
sensor 3. Consequently, the actual sweep-type fingerprint sensor 3
should be located within the range from the coordinates (2, 2) to
(32, 24), preferably located within the range from the coordinates
(2, 2) to (24, 24), and more preferably located within the range
from the coordinates (2, 2) to (24, 16).
[0035] FIG. 9 is a top view showing a card device according to a
first embodiment of the invention. As shown in FIG. 9, the
sweep-type fingerprint sensor 3 is disposed in a rectangular
low-stress region 7. The low-stress region 7 is the region defined
by the above-derived coordinates of (2, 2) and (32, 24).
Consequently, the dimension of the low-stress region 7 is "safety
length L (=30 mm)*safety width W (=22 mm)," and the shortest
distance from the low-stress region 7 to the short side 5 and the
long side 4 is 2 mm.
[0036] In this embodiment, the sweep-type fingerprint sensor 3 is
parallel to the long side 4. That is, the fingerprint sensing
surface 6 is configured such that a finger sweeps across it in a
direction 9, wherein the direction 9 and each long side 4 define an
angle substantially equal to 90 degrees.
[0037] FIG. 10 is a top view showing a card device according to a
second embodiment of the invention. As shown in FIG. 10, the
sweep-type fingerprint sensor 3 is also disposed in the low-stress
region 7. What is different from the first embodiment is that the
sweep-type fingerprint sensor 3 of the second embodiment is
parallel to the short side 5. That is, the fingerprint sensing
surface 6 is configured such that the finger sweeps across it in
the direction 9, wherein the direction 9 and each long side 4
define an angle substantially equal to 0 degrees.
[0038] FIG. 11 is a top view showing a card device according to a
third embodiment of the invention. As shown in FIG. 11, the
sweep-type fingerprint sensor 3 is also disposed in the low-stress
region 7. What is different from the first embodiment is that the
fingerprint sensing surface 6 of the third embodiment is configured
such that the finger sweeps across it in the direction 9, wherein
the direction and each long side 4 define an angle substantially
equal to 45 degrees.
[0039] FIG. 12 is a top view showing a card device according to a
fourth embodiment of the invention. As shown in FIG. 12, the
sweep-type fingerprint sensor 3 is also disposed in the low-stress
region 7. What is different from the first embodiment is that the
fingerprint sensing surface 6 of the fourth embodiment is
configured such that the finger sweeps across it in the direction
9, wherein the direction 9 and each long side 4 define an angle,
which is substantially equal to that defined by a diagonal 8 of the
substrate 2 and each long side 4.
[0040] FIG. 13 is a partially cross-sectional view showing a card
device according to a fifth embodiment of the invention. In this
embodiment, a groove 10 is formed on the substrate 2, and the
sweep-type fingerprint sensor 3 is located in the groove 10. The
groove 10 is for guiding the finger to put therein and guiding the
finger to sweep across the sweep-type fingerprint sensor 3. As a
result, the groove may guide the user to use the sweep-type
fingerprint sensor 3 for fingerprint reading rapidly.
[0041] In order to solve the prior art drawbacks, the invention
provides a card device having a sweep-type fingerprint sensor
located in the low-stress region as the criterion for actual
applications. Thus, the cost may be greatly reduced, the
application field of this device may be widened, and the problem of
chip damage owing to the stress can be overcome. Furthermore, the
invention also provides a guiding groove for the sweep-type
fingerprint sensor so as to make the user find the sensing surface
of the sweep-type fingerprint sensor rapidly. In addition, the
groove may also guide the finger to sweep in a straight line
direction as possible as it can, so as to simplify the subsequent
image reconstruction operations.
[0042] While the invention has been described by way of examples
and in terms of preferred embodiments, it is to be understood that
the invention is not limited to the disclosed embodiments. To the
contrary, it is intended to cover various modifications. Therefore,
the scope of the appended claims should be accorded the broadest
interpretation so as to encompass all such modifications.
* * * * *